Vehicle anti-rollover system

ABSTRACT

A work vehicle is provided having a first pair of wheels mounted to a vehicle body via a fixed axle and a second pair of wheels mounted to the vehicle body via a pivotable axle. The work vehicle includes an anti-rollover system with at least two load sensors mounted at an axle housing near different ones of the first pair of wheels to measure a downward force borne by each respective wheel, the at least two load sensors being operationally connected to a processor. The processor is configured to send anti-rollover commands to the anti-rollover system based on signals received from the at least two load sensors.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national stage of PCT Application No.PCT/EP2014/061135, entitled “VEHICLE ANTI-ROLLOVER SYSTEM”, filed on May28, 2014, which claims priority from and the benefit of Italian PatentApplication Serial No. MO2013A000156, filed on May 30, 2013. Each of theforegoing applications is hereby incorporated by reference in itsentirety.

The present invention relates to a system and method for preventingrollover of work vehicles, in particular agricultural vehicles.

An agricultural vehicle is typically provided with wheels resting on theground. The wheels are connected to the vehicle body via a front axleand a rear axle arranged transversely to the movement direction of thevehicle. The distribution of the weight of the vehicle on the axlesvaries according to use, the rest configuration on the ground, theimplement connected to the vehicle, the load on board, both fixed andvariable or movable, and only in a few operating circumstances it isconstructionally predetermined.

In agricultural vehicles, the axles typically do not haveshock-absorbing suspension means, but are rigid. Therefore, in anattempt to distribute the load as uniformly as possible on the groundbetween the wheels of the same axle, one of the two axles is rotateably(or pivotably) connected to the body of the vehicle, in such a manner asto be able to oscillate, i.e. rotate, with respect to a longitudinalaxis of the vehicle. Thereby the pivotable axle is able to follow, atleast partially, the unevenness of the ground, which would otherwiseforce the vehicle to rest irregularly on the ground, which would alterthe loads of the wheels on the ground, until, for example, a wheeldetaches from the ground.

In tractors the front axle is typically rotateably connected to thevehicle body because in general, the front axle bears less loads thanthe rear axle. In such configuration, the angular position of thevehicle is determined by the position of the rear axle, which is fixedwith respect to the vehicle. The front axle can perform oscillationswithin a limited oscillation magnitude around the longitudinal axis ofthe vehicle. Thereby the front wheels are enabled to follow theunevenness of the ground, independently of the angular position of thevehicle which is determined by the unevenness of the ground.

In, e.g., a combine harvester the rear axle is typically pivotable andthe front axle fixed. In the following, a tractor with an unsuspendedpivotable front axle will be described and a fixed rigid rear axle willbe used as an example. It is, however, to be noted that the problems andsolutions described are similarly applicable to vehicles with apivotable rear axle and vehicles in which the pivotable axle issuspended (either dependently or independently).

The oscillation magnitude is typically limited by suitable end-of-strokestops placed at the location of the front wheels. On average, a rotationof the front axle around the longitudinal axis of the vehicle between+10 degrees and −10 degrees is allowed. Thereby, the total rotationalfreedom is about 20 degrees.

As a result of the configuration of rigid rear axle and oscillatingfront axle, the vehicle structure is very similar to that of athree-wheeled vehicle, with two rear and one front resting point, atleast for all positions of the front axle for which the limitation tothe oscillation of the front axle has not intervened. Thus, the frontaxle does not contribute in any way to rollover resistance (at leastwhen end-of-stroke stops have not been reached in the oscillation) sinceit centrally supports the vehicle body.

Stability of the vehicle on sloping ground is critical. Such stabilitycan be negatively influenced by implements connected to the vehicle.This makes it dangerous to drive the vehicle on sloping ground,especially during lifting and transporting of very heavy loads, sincethere is a great risk of the vehicle overturning. Such overturninggenerally has severe consequences, which are often mortal for the driverof the vehicle.

EP2444304 proposes a device and a method for increasing the stability ofthe vehicle, thus reducing the risk of the vehicle overturning incritical working conditions. It discloses a system for preventingoverturning comprising at least one actuator, for example adouble-acting hydraulic actuator, interposed between the front axle andthe body of the vehicle. The actuator is able to exert controllableforces on the front axle in such a manner as to contrast the rotation ofthe front axle with respect to the body of the vehicle. In EP2444304,rollover is detected using a complex combination of sensors. Thesesensors typically measure the angular position or angular accelerationof the vehicle. Via the measurements of angular position and/oracceleration, rollover is detected, and in a further step corrected viathe actuator.

A drawback of the known anti-rollover system is that angular positionsensors or angular acceleration sensors are typically inaccurate whenapplied to an agricultural vehicle. Namely, an agricultural vehicle inoperation generates a substantial amount of high frequency and lowfrequency vibrations. These vibrations are continuously picked up by theangular position sensor and/or angular acceleration sensor, disturbingthe output of these sensors. Thus the sensitivity of the sensors,necessary to correctly detect rollover in an early stage, increases thesensitivity to the disturbance by vehicle vibrations. Although theseangular position sensors and/or angular acceleration sensors work verywell in a laboratory to detect rollover (in ideal circumstances) in areal life environment, the agricultural vehicles movements andvibrations make rollover detection inaccurate.

It is an object of the present invention to provide an agriculturalvehicle with an anti-rollover system that is more accurate.

To this end, the invention proposes a work vehicle having a first pairof wheels mounted to a vehicle body via a fixed axle and a second pairof wheels mounted to said vehicle body via a pivotable axle, the vehiclecomprising an anti-rollover system comprising at least two load sensormeans mounted at an axle housing near at least two different ones of thefirst pair of wheels, to measure a downward force borne by therespective wheel, the load sensor means being operationally connected toa processor, wherein the processor is configured to send anti-rollovercommands to the anti-rollover system, based on signals received fromsaid at least two load sensor means.

In FIG. 3, a wheel and the adjacent part of the axle housing are shown.Because of its trumpet-like shape, the part of the axle housing close toeach wheel is, from here on, called the ‘trumpet’. It is to be notedthat the invention is, however, not limited to trumpet-shaped axlehousings. Load sensor means are known to be both highly accurate androbust. By providing two load sensor means to the agricultural vehicleat trumpets of different wheels thereof, gives an indication on the loadthat is borne by these wheels. In magnitude, these measured loadsprovide no significant information regarding rollover (since themagnitude of load borne by the wheels is highly dependent on theimplement that is connected to the vehicle and on the working intensityof the vehicle). However, a difference in magnitude indicates adifference in load that is borne by the different wheels, and therebyprovides early stability information (before rollover can be sensed, adifference in load magnitude can be detected). Alternatively, theminimum load value is used for determining the stability of the vehicle.When the load value at at least one of the wheels falls below a certainthreshold, this may be an indication that there is a significantroll-over risk.

When one load sensor means is placed at the trumpet of the left rearwheel of the agricultural vehicle and another load sensor means isplaced in a similar manner near the right rear wheel trumpet of theagricultural vehicle, a comparison is indicative of the left-rightvehicle load distribution. A surprising advantage of using load sensormeans to detect vehicle stability, instead of using angular positionsensors, or angular acceleration sensors, is that before the vehiclestart tilting over (whereby the angular position of the vehiclechanges), an instability can be detected by an uneven load distribution.This allows an anti-rollover system to act on the vehicle on a muchearlier stage when load sensor means are used to measure a vehicleinstability.

In a preferred embodiment, the anti-rollover system comprises a pivotcontrol system with at least one actuator extending between the vehiclebody and the pivotable axle in such a manner that the actuator isprovided to create a torque between the pivotable axle and the vehiclebody and wherein said anti-rollover commands comprise at least anactuating signal for said actuator.

By actively pushing the vehicle body away from, or pulling it towards,one of the ends of the pivotable axle, the center of gravity of thevehicle body is moved and the balance may be restored.

Alternatively, the anti-rollover commands may cause and/or preventbraking, accelerating and/or steering of one or more of the wheels inorder to improve the vehicle balance. As a further alternative, thecenter of gravity of the vehicle may be moved relative to the axles byway of adjusting a position of a movable mass.

In most agricultural vehicles, the fixed axle is the rear axle and thefront axle is the pivotable one In such a configuration, the load sensormeans are preferably provided at least at the rear wheel trumpets, suchthat the downward force on the rear wheels is indicative of theleft-right stability of the vehicle. Providing the load sensors at therear wheel trumpet provides a load measurement that is indicative of thedownward load borne by the rear wheels. Based on this indication,anti-rollover commands can be generated to prevent rollover of thevehicle.

Preferably, the anti-rollover system comprises at least one actuatorextending between the vehicle body and the pivotable axle in such amanner that the actuator is provided to push the respective wheel in adirection away from the vehicle frame, wherein said processor isoperationally connected to said at least one actuator, and wherein saidanti-rollover commands comprise at least an actuating signal to saidactuator. By pushing a wheel away from the vehicle frame, the wheel ispushed downward. Thereby, the downward load borne by the wheel isenlarged. Since the total weight of the vehicle remains unchanged,bearing a higher load via a predetermined wheel results in lower loadsto be borne by the other wheels. In this manner, the balance of thevehicle can be changed. Thereby rollover can be prevented.

Preferably, a rear pair of wheels of the vehicle is formed by said firstpair of wheels and is suspended via the fixed axle in a substantiallyrigid manner to said vehicle body so that a relative position of saidrear pair of wheels with respect to the vehicle body is predetermined,and a front pair of wheels of the vehicle is formed by said second pairof wheels and is suspended via said pivotable axle that is hinginglyconnected to the vehicle body in such a manner that the front pair ofwheels are movable with respect to the body in an upward and downwarddirection. Agricultural vehicles are generally built with fixed rearwheels and suspended front wheels. Therefore the invention can beapplied to such agricultural vehicle by mounting the actuator to thefront wheel axles (which are the second pair of wheel supporting arms).

Preferably, the vehicle frame comprises three supporting zones, twosupporting zones being located at the rear end of the frame each one atthe location of a rear wheel so that each rear wheel supports thevehicle frame at a respective one of the two supporting zones, and afurther supporting zone being located centrally at the front end of theframe, wherein the front wheel supporting arms further comprise asupporting element that is hingingly connected to said furthersupporting zone to be rotatable around an axis that is substantiallyparallel to a forward driving direction of the agricultural vehicle,wherein the actuator is connected to at least one of the supportingelement and the front wheel supporting arms. The configuration ofagricultural vehicles is such that its supporting structure is verysimilar to that of a three-wheeled vehicle. In such configuration, byacting on the front wheel, the central front supporting zone can bevirtually shifted to the left or to the right thereby influencing thestability of the vehicle. In this manner, rollover can be prevented.

Preferably, the actuator comprises two single-acting actuators, eachactuator being provided to act on a different one of the front wheeltrumpets. Alternatively, the actuator is formed as a double-actinghydraulic cylinder. This allows influencing the stability of theagricultural vehicle in two directions (left and right).

Preferably, said actuating signal to said actuator is provided toinstruct the actuator to counteract on an imbalance measured betweensaid two load sensor means. By counteracting on a measured imbalance(difference in magnitude between the two load sensor means), thestability is enhanced and thereby rollover is prevented.

Preferably, the processor comprises a comparator for comparing the loadsmeasured by the load sensor means and for determining a difference inmeasured load. By comparing the sensor outputs of the load sensor means,a difference can be detected which is indicative of a pre-rolloverposition (wherein the vehicle body starts leaning over to one side,resulting in a higher load on the wheels located at that side).

Preferably, the work vehicle is an agricultural vehicle.

The invention further relates to an anti-rollover system for a workvehicle, the anti-rollover system comprising at least two load sensormeans operationally connected to a processor, wherein the processor isconfigured to send anti-rollover commands to wheels of the work vehicle,based on signals of said at least two load sensor means, wherein theanti-rollover system is adapted to be mounted in a work vehicle toobtain a work vehicle according to the invention. Preferably theanti-rollover commands comprise at least one of braking instructions,acceleration instructions, steering angle instructions and steering axisactuating instructions.

Preferably the system comprises an actuator provided to be mountedbetween a frame of the work vehicle and a trumpet of a wheel of the workvehicle so that an upward or downward force can be applied to the wheelvia the trumpet. Anti-rollover systems can be built into existingagricultural vehicles, thereby enhancing the stability and preventingrollover of the vehicle.

The invention will now be described in more details with respect to thedrawings illustrating some preferred embodiments of the invention. Inthe drawings:

FIG. 1 shows a principle structure of an agricultural vehicle accordingto an example of the invention;

FIG. 2 illustrates the effect of an intervention of the anti-rolloversystem of the invention; and

FIG. 3 shows an example of a load sensor that can be used in theinvention.

In the drawings a same reference number has been allocated to a same oranalogous element.

In the description, trumpet is defined as a part of the axle housingadjacent each wheel. Because of its trumpet-like shape, this part of theaxle housing is also called the ‘trumpet’. It is to be noted that theinvention is, however, not limited to trumpet-shaped axle housings.supporting arm. The trumpet is typically mounted between the vehiclebody and the wheel. The trumpet is typically a supporting element inwhich the driving or driven shaft is borne via roller bearings.

Agricultural vehicles 1 are designed to be used on a rough terrain. Arough terrain is a terrain with an uneven ground surface and/or unstableground surface. An unstable ground surface is typically the result offluid, semi-fluid or viscous ground surface materials such as dirt, sandor similar materials. An agricultural vehicle is provided with largewheels compared to regular vehicles, so that the agricultural vehiclecan move well on these rough terrains.

On these rough terrains, as a result of uneven ground surfaces, rolloverof an agricultural vehicle is a known risk. To prevent an agriculturalvehicle from rolling-over, the track width of the vehicle, determined bythe distance between left vehicle wheels and right vehicle wheels isenlarged compared to regular vehicles. However in extreme circumstances,this adaptation might not be enough to prevent rollover. It is an objectof the present invention to provide an agricultural vehicle with a highrollover resistance.

The vehicle 1 comprises a body 2 to which a pair of rear wheels 3 areconnected. The rear wheels 3 are powered by the engine of the vehiclevia a rear driving shaft (not shown) connecting the wheels 3 with thebody 2 in a substantially rigid manner (meaning with no significantsuspension means between the wheel and the body). The vehicle 1 isfurther provided with a pair of front wheels 4 connected to the body 2of the vehicle via a front axle 5. The front axle is hingingly connectedto the vehicle body thereby enabling the front axle 5 to oscillate withrespect to the body 2 around a longitudinal axis of the vehicle, beingan axis that is substantially parallel to the straight moving directionof the vehicle. The oscillation movement of the front axle 5 withrespect to the body 2 is limited by stop elements 6.

Starting from the general principle that a resting body remains in astable equilibrium if the resultant of the forces acting thereon isdirected to the rest and meets the resting surface inside the restingpolygon. In the case of a vehicle 1, if the vehicle is subject to thesingle or combined effects of centrifugal forces (due to curvedtrajectories), of lateral and/or longitudinal slopes, and of externalforces, the reactions of resting on the ground of the single wheels willbe reconfigured as constraints for re-establishing equilibrium. Acombination of these effects might in certain circumstances result in arear wheel lifting up from the ground (prelude to rollover).

It should be noted that, at least until the front axle 5 does not reachthe oscillation end-of-stroke limits defined by the stop elements 6, thestability of the vehicle, in terms of lateral overturning (rollover), isensured only by the rear wheels 3. Namely the hingingly connected frontaxle 5 provides no resistance against lateral roll (due to the hinge).

If the rear wheels 3 rest on a tilted and/or unstable ground surface,the body 2 of the vehicle 1 might rotate with respect to the front axle5 around the hinge connection C. This rotation may cause one of the rearwheels to lift up from the ground. By lifting of one of the rear wheels,the resting triangle (three-wheeled vehicle) degenerates in a restingstraight line. Through the effect of the rotation of the body 2 of thevehicle 1 with respect to the front axle 5 and of the lifting of therear wheel 3, the centre of gravity G of the vehicle rotates around anaxis coinciding with said straight line. Through the effect of saidrotation, the centre of gravity G rises and, simultaneously, movestowards said straight line (being an edge of the resting triangle). Whenthe center of gravity passes the resting straight line, i.e. exits fromthe resting triangle, the vehicle 1 overturns.

The rollover dynamics of the vehicle 1 are nevertheless influenced bythe fact that the oscillation of the front axle 5 with respect to thebody 2 is limited to a predetermined angle (by the stop elements 6).When the stop elements 6 come into contact with the front axle 5 (whenthe stop elements are mounted on the vehicle body as is shown in thefigure) or with the vehicle body (when the stop elements are mounted onthe front axle as is not shown in the figure), further rotation of thebody 2 of the vehicle 1 with respect to the front axle 5 is prevented.Typically, this occurs before the center of gravity passes the restingstraight line, i.e. before the vehicle 1 has reached limit balancecondition.

When the stop elements 6 prevent further rotation of the front axle 5,the latter becomes a supporting point to the body 2 of the vehicle 1. Asa result, the resting triangle is reconfigured since the earlier centralfront supporting zone is shifted towards the location of the stopelement. The balance of the vehicle will thus be ensured up to themoment that the center of gravity exceeds the newly defined restingtriangle. Thus apparently the stop elements 6 seem to be able to preventoverturning of the vehicle. Nevertheless, it must be considered thatrotation of the body 2 of the vehicle 1 with respect to the front axle 5is a dynamic phenomenon. This means that when the stop elements comeinto contact with the front axle 5, locking the rotation of the body 2of the vehicle 1 with respect to said front axle 5, the inertia forcesacting on the vehicle can continue the side rotation of the vehicle,still causing overturning of the vehicle 1.

The anti-rollover system of the invention comprises at least two loadsensor means that are mounted at the location of different wheels of theagricultural vehicle 1. Preferably, the anti-rollover system comprises aload sensor near each of the four wheels 3, 4 of the agriculturalvehicle. In this manner, a downward load borne by each wheel can bemeasured and used to determine the stability of the vehicle. Differentload measurement means and configurations can be used to form the loadsensor means useable in the invention. The load sensor means useable inthe invention is at least suitable for, and mounted at the location of awheel of the agricultural vehicle in such a manner that a load ismeasured that gives an indication of the downward load that is borne bythe respective wheel. The load sensor means can comprise multipleindividual load sensors, for example one mounted at the upper side andanother at the lower side of the trumpet of the agricultural vehicle tothereby enhance the measured results.

FIG. 2 shows the effect of the anti-rollover system according to anembodiment of the invention. In the figure, the front wheels and rearwheels of an agricultural vehicle 1 are shown. Thereby, the agriculturalvehicle has a configuration wherein the rear wheels 3 are connectedsubstantially rigid to the vehicle frame. The front wheels 4 arehingingly connected to the frame such that the front wheels axle 5 canoscillate with respect to the vehicle frame. Therefore, without actuatoracting on the front axle 5, and without the front axle 5 reaching ortouching the stop elements, the load division between the two frontwheels is always 50-50 (meaning that the wheels bear an equal load).

FIG. 2A shows a situation where the agricultural vehicle is in a stableposition. The rear wheels show how the load at the rear end of theagricultural vehicle is substantially equally divided between left andright (being a 40-60 division). In such situation, the agriculturalvehicle stand stable and there is low risk of turnover.

FIG. 2B shows a situation where there is a substantial difference inload borne by the left and right rear wheels. In the example, the leftrear wheel (on the right-hand side of the figure) bears 80% of the loadwhile the right rear wheel bears only 20% of the load. Such situationmight occur when the agricultural vehicle is placed on a laterally steepunderground. Such load division indicates that there is a high risk ofrollover. In such situation, the load division of the front wheels issubstantially equal to 50-50. The reason for this is that the frontwheels are hingingly connected to the vehicle frame, able to oscillatearound hinge point C. An unequal load division between the two frontwheels would result in the front wheel axle 5 hinging towards a newbalance point (where the load is equally divided). This processcontinues as long as the front wheel axle 5 can freely rotate. As aresult, the stability of the agricultural vehicle is only determined bythe rear wheels.

FIG. 2C shows a situation wherein the anti-rollover system of thepresent invention is activated. The starting situation is the situationshown in FIG. 2B. Thus in FIG. 2C, the same environmental and externalconditions apply to the agricultural vehicle as in FIG. 2B. Theanti-rollover system detects the difference in load measured between thetwo rear wheels (80-20) and activates the pivot control system 7 tocompensate the unbalance. Alternatively, the minimum load value is usedfor determining the stability of the vehicle. When the load value at atleast one of the wheels falls below a certain threshold, this may be anindication that there is a significant roll-over risk. When a roll-overrisk is detected, the actuator 8 applies a force to the front axle 5 topush the left front wheel (shown on the right hand side of the figure)downward, away from the vehicle frame. As a result of the force applied,the equal load distribution between the front wheels is shifted towardsthe actuated wheel. FIG. 2C shows how the load is divided 60-40 betweenthe front wheels because the actuator is activated. As a result, theload difference between the rear wheels is (at least partially)compensated and brought back to a 70-30 division. This will bring theagricultural vehicle back into a more stable position thereby preventingrollover of the vehicle. In this regard, it is noted that rollover canonly be detected by angular sensors once a rear wheel loses contact withthe ground surface. According to the present invention, rollover can bedetected at a very early stage, when stability of the agriculturalvehicle decreases.

The anti-rollover system comprises at least one actuator 8, for examplea double-acting hydraulic actuator, interposed between the front axle 5and the body of the vehicle. The actuator is able to exert controllableforces on the front axle in such a manner as to counteract on therotation of the front axle with respect to the body of the vehicle. Theactuator typically comprises an actuator body 8, connected to the body 2of the vehicle 1 by a first rotating connection 11, and a stem 9connected to the front axle 5 via a second rotating connection 10.

The stability of the vehicle 1 can be increased by limiting movement ofthe centre of gravity G of the vehicle 1 to the resting polygon on theground (preferably before the stop elements 6 come into contact with thefront axle 5) Thereby, the risk of overturning of the vehicle can besubstantially reduced.

The anti-rollover system comprises at least one actuator 8, for examplea double-acting hydraulic actuator, interposed between the front axle 5and the body 2 of the vehicle 1. The actuator 8 comprises an actuatorbody, connected to the body 2 of the vehicle 1 by a first rotatingconnection 11, and a stem 9 connected to the front axle 5 via a secondrotating connection 10. The actuator 8 is able, according to a firstintervention mode, to exert controllable forces on the front axle 5 insuch a manner as to counteract the rotation of the front axle 5 withrespect to the body 2 of the vehicle 1.

The actuator 8 can be provided to operate according to a secondintervention mode, depending on the overturning risk conditions. In suchmode, the actuator is suitable for locking the front axle 5 in apredetermined angular position with respect to the body 2 of the vehicle1, and thus fixing the position of the front wheels 4 with respect tosaid body 2.

The first or the second intervention mode are selectable by the systembased on different input factors.

The maximum stroke of the stem 9 of the actuator 8 is dimensioned insuch a manner as not to limit the maximum angle of oscillation of thefront axle 5. Further, in conditions of normal operating stability ofthe vehicle 1, the actuator 8 is configured not to oppose significantresistance to the oscillation of the front axle 5. If an additionalactuator is used to push on and/or pull at the other end of thepivotable axle 5, the actuators 8 may additionally be used as part of asuspension system for damping oscillations of the pivotable axle 5. Thetwo actuators 8 may be hydraulically coupled to each other.

It should be noted that the dual-action actuator device 8 can bereplaced by two single-action actuator devices, connected to the body 2of the vehicle and to the front axle 5 on opposite sides with respect tothe central axis of the vehicle 1. In this case, when the risk ofoverturning occurs, the system according to the invention activates theactuator located on the side where the overturning risk exists. Theforce applied to the front axle 5 by the single-action actuator devicesis always directed towards the front axle 5. Also the two single-actionactuator devices may simultaneously be part of a suspension system for asuspended pivotable axle and may or may not be hydraulically coupled toeach other.

It is to be noted that the anti-rollover system described above can alsobe used with independently suspended pivotable axles in which the leftand right ends of the pivotable axle can make different angles with thevehicle body 2.

FIG. 3 shows an example of a load sensor 20 placed at the location of arear wheel 3. It will be clear that in a similar manner, a load sensorcan be placed at the location of a front wheel 4. The load sensor 20according to the example of FIG. 3 comprises multiple (a total of six)strain gauges 22, 23, 24, 25, 26 and 27. The strain gauges are mountedto the upper side and to the lower side of the supporting arm 21 of therear wheel 3. Essentially only one strain gauge is sufficient to get anindication of the load borne by the wheel 3. For more accurate results,two strain gauges are provided symmetrically with respect to the axleaxis, one on the upper side and one on the lower side of the axle. Whenmultiple strain gauges are placed at different distances from the wheel,it is possible to extract the downward force F from the results of theload measurement without requiring any additional information.

Advantageously, the work vehicle 1 further comprises an inclinationsensor (not shown) provided for measuring the angular position of thework vehicle. The inclination sensor can be used for deriving thevertical component from the total load measured by the load sensors. Theoutput of the inclination sensor is operationally connected to theprocessor. The processor can also take the results of the inclinationsensor into account when anti-rollover instructions are generated.Preferably, the actuator is only instructed to act on the front shaftwhen the imbalance measured by the load sensors is oriented in the samedirection as the inclination measured by the inclination sensor. Forexample when the load at the right side of the work vehicle is 70% ofthe total load and the work vehicle inclines to the right, then theactuator is instructed to act on the front shaft to counter the measuredimbalance.

The example of FIG. 3 proved to be very useful in extracting thedownward force F from the loads measured by the strain gauges. The sixstrain gauges 22, 23, 24, 25, 26 and 27 according to the example aremounted symmetrical with respect to the axle, three at the upper sideand three at the lower side of the axle (in the further explanationreferred to as three pairs of strain gauges). One pair of strain gauges24, 27 is located close to the wheel 3 mounting surface. A second pair23, 26 of strain gauges is located at one side and close to a lateralmounting zone 28 (lateral with respect to the axle direction) of theaxle. A third pair 22, 25 of strain gauges is located at the other sideand close to the lateral mounting zone 28 of the axle. Thereby,preferably the distance between the center of the lateral mounting zone28 and the second pair of strain gauges 23, 26 is substantially equal tothe distance between the center of the lateral mounting zone 28 and thethird pair of strain gauges 22, 25. This allows the second pair andthird pair of strain gauges to eliminate the impact of the lateral forceapplied to the axle from the measurements. Preferably the distancebetween the first and second pair of strain gauges is different from thedistance between the second and third pair of strain gauges and isfurthermore different from the distance between the first and third pairof strain gauges. This allows eliminating lateral forces applied to thewheel 3.

It is further advantageous to enable the system for preventingoverturning according to the invention, such that it is able to bedriven manually by the driver of the vehicle, who manually commands andadjusts the actuator 8 by a suitable driving device that is manuallyactivatable and provided in the driver cab. Manual driving of the systemfor preventing overturning according to the invention is useful, forpreventive purposes, in the case of travelling on inclined ground thatis inclined transversely to the movement direction, the system in allcases activating automatically in the case of a high or extremely highoverturning risk. Further, the system for preventing overturningaccording to the invention can be used for auxiliary services, such aslifting a wheel, for example to replace the wheel in the event of apuncture or for maintenance.

The invention claimed is:
 1. A work vehicle having a first pair ofwheels mounted to a vehicle body via a fixed axle and a second pair ofwheels mounted to the vehicle body via a pivotable axle, the workvehicle comprising an anti-rollover system comprising at least two loadsensors mounted at an axle housing near different ones of the first pairof wheels to measure a downward force borne by each respective wheel ofthe first pair of wheels, the at least two load sensors beingoperationally connected to a processor, wherein the processor isconfigured to send anti-rollover commands to the anti-rollover systembased on signals received from the at least two load sensors, whereinthe anti-rollover system comprises a pivot control system with at leastone actuator that extends from the vehicle body at a first end to thepivotable axle at a second end, the at least one actuator is configuredto create a torque about a longitudinal axis between the pivotable axleand the vehicle body, and the anti-rollover commands comprise at leastan actuating signal to the at least one actuator.
 2. The work vehicleaccording to claim 1, wherein the at least one actuator comprises twosingle-acting actuators, each single-acting actuator being provided toact on a different end of the pivotable axle.
 3. The work vehicleaccording to claim 1, wherein the at least one actuator is formed as atleast one double-acting hydraulic cylinder.
 4. The work vehicleaccording to claim 1, wherein the fixed axle is a rear axle and thepivotable axle is a front axle of the work vehicle.
 5. The work vehicleaccording to claim 1, wherein the pivotable axle is a suspended axle. 6.The work vehicle according to claim 1, wherein the processor isconfigured to send the anti-rollover commands to a braking system, wheeldrive system, or steering system.
 7. The work vehicle according to claim1, wherein the actuating signal for the at least one actuator isprovided to instruct the at least one actuator to counteract animbalance measured between the at least two load sensors.
 8. The workvehicle according to claim 1, wherein the processor comprises acomparator configured to compare loads measured by the at least two loadsensors and to determine a difference in the loads.
 9. The work vehicleaccording to claim 1, wherein the work vehicle is an agriculturalvehicle.
 10. The anti-rollover system according to claim 1 for use inthe work vehicle.
 11. A pivot control system with at least one actuatorthat extends from a vehicle body at a first end to a pivotable axle at asecond end, wherein the at least one actuator is configured to create atorque about a longitudinal axis between the pivotable axle and thevehicle body, and a processor configured to send an actuating signal tothe at least one actuator based on signals received from at least twoload sensors.
 12. At least one tangible, non-transitory,machine-readable medium, comprising machine-readable instructions to:measure, via at least two load sensors mounted at an axle housing neardifferent ones of a first pair of wheels, a downward force borne by eachrespective wheel of the first pair of wheels; generate anti-rollovercommands based on signals received from the at least two load sensors;and send the anti-rollover commands to an anti-rollover system having atleast one actuator coupled to a pivotable axle at a first end and avehicle body of the work vehicle at a second end, wherein theanti-rollover commands are configured to cause the at least one actuatorto create a torque about a longitudinal axis between the pivotable axleand the vehicle body.